ABSTRACT
We present a joint strong lensing and stellar dynamical framework for future time-delay cosmography purposes. Based on a pixelated source reconstruction and the axisymmetric Jeans equations, ...we are capable of constraining cosmological distances and hence the current expansion rate of the Universe (H0) to the few per cent level per lens, when high signal-to-noise integral field unit (IFU) observations from the next generation of telescopes become available. For illustrating the power of this method, we mock up IFU stellar kinematic data of the prominent lens system RXJ1131−1231, given the specifications of the James Webb Space Telescope. Our analysis shows that the time-delay distance (DΔt) can be constrained with 3.1 per cent uncertainty at best, if future IFU stellar kinematics are included in the fit and if the set of candidate model parametrizations contains the true lens potential. These constraints would translate to a 3.2 per cent precision measurement on H0 in flat ΛCDM cosmology from the single lens RXJ1131−1231, and can be expected to yield an H0 measure with ≤2.0 per cent uncertainty, if similar gains in precision can be reached for two additional lens systems. Moreover, the angular diameter distance (Dd) to RXJ1131−1231 can be constrained with 2.4 per cent precision, providing two distance measurements from a single lens system, which is extremely powerful to further constrain the matter density (Ωm). The measurement accuracy of Dd, however, is highly sensitive to any systematics in the measurement of the stellar kinematics. For both distance measurements, we strongly advise to probe a large set of physically motivated lens potentials in the future, to minimize the systematic errors associated with the lens mass parametrization.
ABSTRACT
We present the lens mass model of the quadruply-imaged gravitationally lensed quasar WFI2033 − 4723, and perform a blind cosmographical analysis based on this system. Our analysis combines ...(1) time-delay measurements from 14 yr of data obtained by the COSmological MOnitoring of GRAvItational Lenses (COSMOGRAIL) collaboration, (2) high-resolution Hubble Space Telescope imaging, (3) a measurement of the velocity dispersion of the lens galaxy based on ESO-MUSE data, and (4) multi-band, wide-field imaging and spectroscopy characterizing the lens environment. We account for all known sources of systematics, including the influence of nearby perturbers and complex line-of-sight structure, as well as the parametrization of the light and mass profiles of the lensing galaxy. After unblinding, we determine the effective time-delay distance to be $4784_{-248}^{+399}~\mathrm{Mpc}$, an average precision of $6.6{{\ \rm per\ cent}}$. This translates to a Hubble constant $H_{0} = 71.6_{-4.9}^{+3.8}~\mathrm{km~s^{-1}~Mpc^{-1}}$, assuming a flat ΛCDM cosmology with a uniform prior on Ωm in the range 0.05, 0.5. This work is part of the H0 Lenses in COSMOGRAIL’s Wellspring (H0LiCOW) collaboration, and the full time-delay cosmography results from a total of six strongly lensed systems are presented in a companion paper (H0LiCOW XIII).
The local expansion rate of the Universe is parametrized by the Hubble constant, Formula: see text, the ratio between recession velocity and distance. Different techniques lead to inconsistent ...estimates of Formula: see text Observations of Type Ia supernovae (SNe) can be used to measure Formula: see text, but this requires an external calibrator to convert relative distances to absolute ones. We use the angular diameter distance to strong gravitational lenses as a suitable calibrator, which is only weakly sensitive to cosmological assumptions. We determine the angular diameter distances to two gravitational lenses, Formula: see text and Formula: see text megaparsec, at redshifts Formula: see text and 0.6304. Using these absolute distances to calibrate 740 previously measured relative distances to SNe, we measure the Hubble constant to be Formula: see text kilometers per second per megaparsec.
Context.
Persistent tension between low-redshift observations and the cosmic microwave background radiation (CMB), in terms of two fundamental distance scales set by the sound horizon
r
d
and the ...Hubble constant
H
0
, suggests new physics beyond the Standard Model, departures from concordance cosmology, or residual systematics.
Aims.
The role of different probe combinations must be assessed, as well as of different physical models that can alter the expansion history of the Universe and the inferred cosmological parameters.
Methods.
We examined recently updated distance calibrations from Cepheids, gravitational lensing time-delay observations, and the tip of the red giant branch. Calibrating the baryon acoustic oscillations and type Ia supernovae with combinations of the distance indicators, we obtained a joint and self-consistent measurement of
H
0
and
r
d
at low redshift, independent of cosmological models and CMB inference. In an attempt to alleviate the tension between late-time and CMB-based measurements, we considered four extensions of the standard ΛCDM model.
Results.
The sound horizon from our different measurements is
r
d
= (137 ± 3
stat.
± 2
syst.
) Mpc based on absolute distance calibration from gravitational lensing and the cosmic distance ladder. Depending on the adopted distance indicators, the combined tension in
H
0
and
r
d
ranges between 2.3 and 5.1
σ
, and it is independent of changes to the low-redshift expansion history. We find that modifications of ΛCDM that change the physics after recombination fail to provide a solution to the problem, for the reason that they only resolve the tension in
H
0
, while the tension in
r
d
remains unchanged. Pre-recombination extensions (with early dark energy or the effective number of neutrinos
N
eff
= 3.24 ± 0.16) are allowed by the data, unless the calibration from Cepheids is included.
Conclusions.
Results from time-delay lenses are consistent with those from distance-ladder calibrations and point to a discrepancy between absolute distance scales measured from the CMB (assuming the standard cosmological model) and late-time observations. New proposals to resolve this tension should be examined with respect to reconciling not only the Hubble constant but also the sound horizon derived from the CMB and other cosmological probes.
We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part ...of the Strong Lensing Legacy Survey. We combine these data with photometric and lensing measurements presented in the companion paper III and with lenses from the Sloan Lens Advanced Camera for Surveys and Lenses Structure and Dynamics surveys to investigate the cosmic evolution of the internal structure of massive early-type galaxies over half the age of the universe. This result is obtained by combining our measured dependencies of gamma ' on z, M sub(*), R sub(eff) with the evolution of the R sub(eff)-M sub(*) taken from the literature, and is broadly consistent with current models of the formation and evolution of massive early-type galaxies. Detailed quantitative comparisons of our results with theory will provide qualitatively new information on the detailed physical processes at work.
We present Hubble Space Telescope (HST) imaging data and Canada-France-Hawaii Telescope (CFHT) near-infrared ground-based images for the final sample of 56 candidate galaxy-scale lenses uncovered in ...the CFHT Legacy Survey as part of the Strong Lensing in the Legacy Survey project. Based on the analysis of systematic uncertainties and comparison with inference based on different methods, we estimate that our Einstein radii are accurate to ~3%. HST imaging provides a much higher success rate in confirming gravitational lenses and measuring their Einstein radii than CFHT imaging does. Lens modeling with ground-based images, however, when successful, yields Einstein radius measurements that are competitive with space-based images. The redshifts of the main deflector span a range 0. 3 < or =, slant z sub(d) < or =, slant 0.8, which nicely complements low-redshift samples like the Sloan Lens ACS survey and thus provides an excellent sample for the study of the cosmic evolution of the mass distribution of ETGs over the second half of the history of the universe.
We investigate the local and line-of-sight (LOS) overdensities of strong gravitational lens galaxies using wide-area multiband imaging from the Hyper Suprime-Cam Subaru Strategic Program. We present ...41 new definite or probable lens candidates discovered in Data Release 2 of the survey. Using a combined sample of 87 galaxy-scale lenses out to a lens redshift of zL ∼ 0.8, we compare galaxy number counts in LOSs toward known and newly discovered lenses in the survey to those of a control sample consisting of random LOSs. We also compare the local overdensity of lens galaxies to a sample of "twin" galaxies that have similar redshift and velocity dispersion to test whether lenses lie in different environments from similar nonlens galaxies. We find that lens fields contain higher number counts of galaxies compared to the control fields, but this effect arises from the local environment of the lens. Once galaxies in the lens plane are removed, the lens LOSs are consistent with the control sample. The local environments of the lenses are overdense compared to the control sample, and are slightly overdense compared to those of the twin sample, although the significance is marginal. There is no significant evidence of the evolution of the local overdensity of lens environments with redshift.
We present predictions for time delays between multiple images of the gravitationally lensed supernova, iPTF16geu, which was recently discovered from the intermediate Palomar Transient Factory ...(iPTF). As the supernova is of Type Ia where the intrinsic luminosity is usually well known, accurately measured time delays of the multiple images could provide tight constraints on the Hubble constant. According to our lens mass models constrained by the Hubble Space Telescope F814W image, we expect the maximum relative time delay to be less than a day, which is consistent with the maximum of 100 hr reported by Goobar et al. but places a stringent upper limit. Furthermore, the fluxes of most of the supernova images depart from expected values suggesting that they are affected by microlensing. The microlensing timescales are small enough that they may pose significant problems to measure the time delays reliably. Our lensing rate calculation indicates that the occurrence of a lensed SN in iPTF is likely. However, the observed total magnification of iPTF16geu is larger than expected, given its redshift. This may be a further indication of ongoing microlensing in this system.
Strong gravitational lensing and microlensing of supernovae (SNe) are emerging as a new probe of cosmology and astrophysics in recent years. We provide an overview of this nascent research field, ...starting with a summary of the first discoveries of strongly lensed SNe. We describe the use of the time delays between multiple SN images as a way to measure cosmological distances and thus constrain cosmological parameters, particularly the Hubble constant, whose value is currently under heated debates. New methods for measuring the time delays in lensed SNe have been developed, and the sample of lensed SNe from the upcoming Rubin Observatory Legacy Survey of Space and Time (LSST) is expected to provide competitive cosmological constraints. Lensed SNe are also powerful astrophysical probes. We review the usage of lensed SNe to constrain SN progenitors, acquire high-z SN spectra through lensing magnifications, infer SN sizes via microlensing, and measure properties of dust in galaxies. The current challenge in the field is the rarity and difficulty in finding lensed SNe. We describe various methods and ongoing efforts to find these spectacular explosions, forecast the properties of the expected sample of lensed SNe from upcoming surveys particularly the LSST, and summarize the observational follow-up requirements to enable the various scientific studies. We anticipate the upcoming years to be exciting with a boom in lensed SN discoveries.
Abstract
Based on spectroscopy and multiband wide-field observations of the gravitationally lensed quasar HE 0435−1223, we determine the probability distribution function of the external convergence ...κext for this system. We measure the under/overdensity of the line of sight towards the lens system and compare it to the average line of sight throughout the Universe, determined by using the CFHTLenS (The Canada France Hawaii Lensing Survey) as a control field. Aiming to constrain κext as tightly as possible, we determine under/overdensities using various combinations of relevant informative weighting schemes for the galaxy counts, such as projected distance to the lens, redshift and stellar mass. We then convert the measured under/overdensities into a κext distribution, using ray-tracing through the Millennium Simulation. We explore several limiting magnitudes and apertures, and account for systematic and statistical uncertainties relevant to the quality of the observational data, which we further test through simulations. Our most robust estimate of κext has a median value $\kappa ^\mathrm{med}_\mathrm{ext} = 0.004$ and a standard deviation σκ = 0.025. The measured σκ corresponds to 2.5 per cent relative uncertainty on the time delay distance, and hence the Hubble constant H0 inferred from this system. The median $\kappa ^\mathrm{med}_\mathrm{ext}$ value varies by ∼0.005 with the adopted aperture radius, limiting magnitude and weighting scheme, as long as the latter incorporates galaxy number counts, the projected distance to the main lens and a prior on the external shear obtained from mass modelling. This corresponds to just ∼0.5 per cent systematic impact on H0. The availability of a well-constrained κext makes HE 0435−1223 a valuable system for measuring cosmological parameters using strong gravitational lens time delays.
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